The key elements in this type of experiment are selectivity in the excitation and probe mechanisms and polarization information. All of these ingredients have been developed along with ultrafast time resolution to follow the pathways of energy transfer in a number of examples where cofactors are relatively close and the transfer is not necessarily predictable from Fvrster theory. One example is the reaction center in which excitation of the bacteriopheophytin or the accessory bacteriochlorophyll results in rapid energy transfer to the special pair followed by electron transfer. A detailed study of these processes is underway, aimed at characterizing the states of the supermolecule. The interpretation methods involve molecular dynamics simulations. We now have simulations for all the energy transferring states.